Abstract

Photoluminescence and absorption experiments performed on Schott commercial and experimental CdSSe-doped glasses reveal the existence of a pair of narrow electronic states close to the electronic bands. According to a study of the luminescence as a function of the size of the semiconductor spheres, we tentatively interpret them as surface states. A careful analysis of the absorption spectra seems to corroborate this conclusion.

Luminescence spectra of the experimental glasses. The spectra are arbitrarily aligned on peak L1. The absolute position of the spectra can be obtained from Fig. 4. The radii of the semiconductor spheres are written near the curves.

Typical curves of the absorbance and of the second derivative of the absorbance curve obtained for our samples. The two dips in the latter curve reveal the existence of two absorption peaks in the former.

Energy of the two absorption peaks (solid and dashed rectangles) of luminescence peak L1 (pluses) and of luminescence peak L2 (dots) for our samples; the scale for the abscissa is linear for the inverse square radius R of the spheres. The solid line is obtained from the Efros and Efros model13 with an effective electron–hole reduced mass equal to 0.14 times the free-electron mass. The dashed lines are intended only as visual aids.

Schematic representation of the electronic levels as inferred from our experiments. The solid arrows represent absorption processes, and the shaded ones represent luminescence processes. The dashed line corresponds to an impurity level (see text for details).